HSC Survey Results

Scots Bay Survey # 2 Results from 20/05/2024

Survey Details

4 commercial purse seiners conducted this fishing survey on 20/05/2024 starting at 20:00:00, which was 2.65 hours before hide tide.

Lady Melissa and Brunswick Provider each ran two lines in the Main Survey Box, and two in the Eastern Survey Box. Morning Star ran three lines in the Main Survey Box, and Canada 100 ran one line in the Main Survey Box and five lines in the Northern Survey Box..

There was a plankton tow and replicate conducted and CTD cast by Lady Melissa.

No tags were applied during this survey.

Since no fish were caught, no samples were obtained for target strength estimation.

Tides Tables

Tide Schedule for Margaretsville NS, Station #315m Source: www.waterlevels.gc.ca

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for Scots Bay using standardized parallel transects is 29,842mt, and with turnover applied 17,255mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
BP T01 2024-05-20 23:31:00 2024-05-21 01:52:00 -65.230 45.089 -64.762 45.252 SB 41.07 9.44
BP T02 2024-05-21 01:54:00 2024-05-21 02:58:00 -64.757 45.254 -64.549 45.316 SB 17.69 8.96
BP T03 2024-05-21 03:11:00 2024-05-21 04:09:00 -64.565 45.324 -64.757 45.269 SB 16.26 9.08
BP T04 2024-05-21 04:16:00 2024-05-21 06:46:00 -64.767 45.265 -65.238 45.101 SB 41.30 8.92
C1 T01 2024-05-20 22:55:00 2024-05-21 01:25:00 -65.228 45.169 -64.813 45.317 SB 37.91 8.19
C1 T02 2024-05-21 01:27:00 2024-05-21 02:46:00 -64.815 45.320 -65.046 45.251 SB 20.18 8.27
C1 T03 2024-05-21 02:53:00 2024-05-21 04:05:00 -65.049 45.264 -64.825 45.324 SB 19.24 8.66
C1 T04 2024-05-21 04:09:00 2024-05-21 05:19:00 -64.829 45.332 -65.047 45.277 SB 18.60 8.61
C1 T05 2024-05-21 05:25:00 2024-05-21 06:35:00 -65.049 45.289 -64.831 45.338 SB 18.31 8.48
C1 T06 2024-05-21 06:50:00 2024-05-21 07:32:00 -64.869 45.314 -64.995 45.285 SB 10.63 8.20
LM T01 2024-05-20 22:39:00 2024-05-21 00:26:00 -65.233 45.056 -64.719 45.234 SB 45.18 13.68
LM T02 2024-05-21 01:29:00 2024-05-21 02:23:00 -64.710 45.237 -64.549 45.290 SB 13.99 8.40
LM T03 2024-05-21 02:28:00 2024-05-21 03:24:00 -64.550 45.303 -64.718 45.247 SB 14.59 8.44
LM T04 2024-05-21 03:26:00 2024-05-21 06:40:00 -64.726 45.247 -65.290 45.051 SB 49.76 8.31
MS T01 2024-05-20 23:04:00 2024-05-21 01:27:00 -64.825 45.295 -65.234 45.150 SB 37.03 8.39
MS T02 2024-05-21 01:34:00 2024-05-21 03:57:00 -65.231 45.135 -64.791 45.291 SB 39.79 9.01
MS T03 2024-05-21 04:07:00 2024-05-21 06:39:00 -64.776 45.278 -65.231 45.119 SB 41.07 8.75

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
C1 T06 -35.5 -39.144 0.432
C1 T01 -35.5 -45.966 0.090
MS T03 -35.5 -46.525 0.079
MS T02 -35.5 -48.059 0.055
C1 T05 -35.5 -48.134 0.055
C1 T02 -35.5 -49.460 0.040
BP T04 -35.5 -52.663 0.019
MS T01 -35.5 -53.193 0.017
C1 T03 -35.5 -54.826 0.012
BP T03 -35.5 -56.229 0.008
LM T03 -35.5 -56.363 0.008
C1 T04 -35.5 -56.651 0.008
BP T01 -35.5 -60.032 0.004
BP T02 -35.5 -61.095 0.003
LM T02 -35.5 -61.354 0.003
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
Main Box -35.5 518 -49.0883 0.0440 22,672.6500 73.6 76.0 7,587.00 33.46
Northern Box -35.5 85 -46.5881 0.1092 6,616.1446 12.1 22.2 6,900.70 104.30
Eastern Box -35.5 101 -58.1182 0.0055 552.7175 14.3 1.9 164.83 29.82

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by MS, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by C1, at the following location:

Annual Summaries

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
Scots Bay 1 2024-05-05 78,662 NA 2023-05-22 40,856.000 40,856 0 0
Scots Bay 2 2024-05-20 29,842 17,255 2023-06-06 113,767.329 108,783 NA NA
Scots Bay 3 NA NA NA 2023-06-18 34,279.387 15,158 NA NA
Scots Bay 4 NA NA NA 2023-07-02 11,744.776 5,113 NA NA
Scots Bay 5 NA NA NA 2023-07-16 19,282.634 17,575 NA NA
Scots Bay 6 NA NA NA 2023-07-30 4,549.933 1,904 NA NA
Scots Bay 7 NA NA NA 2023-08-13 4,298.806 3,616 NA NA
Scots Bay 9 NA NA NA 2023-09-10 3,053.669 2,916 NA NA
Scots Bay 10 NA NA NA 2023-09-24 3,419.932 2,997 NA NA
Scots Bay 8 NA NA NA 2023-08-27 2,896.659 2,300 NA NA
Scots Bay 11 NA NA NA 2023-10-09 3,387.515 2,971 NA NA
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2023 Scots Bay 241,536.6 204,189 NA NA
2024 Scots Bay 108,504.0 17,255 NA NA

Tagging, Plankton, and CTD Data

Tag Data

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Melissa Lady Melissa
Set Number SB2024-03 SB2024-04
Ground SB SB
Date 20/05/2024 20/05/2024
Wind Direction (km/h) SW SW
Swell (m) 0 0
Air Temp (c) 17 17
Tow Details
Tow Start 18:22:00 18:39:00
Tow End 18:32:00 18:49:00
Start Lat 45.50033 45.05883
End Lat 45.04967 45.07600
Start Lon -65.24867 -65.22367
End Lon -65.22617 -65.21267
Avg Tow Depth (m) 10.76615 14.86889
Speed 5.8 6.3
Heading 92 22
Tide Direction against with
Other Data Collection
Flow Start 806021 863503
Flow End 863503 863508
No. Revolutions 57482 5
Distance (m) 1544.713786 0.134365
Volume 4852.7183590 0.4221076
Secchi Disappear (m) 8 8
Secchi Reappear (m) 7 7

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is SB2024-03, which was against the tide and had an average depth of 10.7661487m. The second tow is SB2024-04, which was with the tide and had an average depth of 14.8688902m.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2024 Scots Bay surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for Scots Bay.

Vessel Performance

Speed

Average vessel speed was 8.98. This is above the 8 knot requirement; vessels are urged to slow down to prevent backscatter noise from interfering with the acoustic data.

Distance

No significant distance was cut from the planned lines; vessels covered the planned area well.